Electronic Alcohol Breath Analyzers

When consumed, alcohol is immediately absorbed into the blood
capillary structure of each successive body tissue and organ it is directly
exposed to. Alcohol's rapid rate of absorption begins in the soft tissues of the
mouth, continues through the esophagus, into the stomach and finally, the small
intestine. Alcohol is somewhat unique in that as it enters the blood stream,
it's chemical structure is not metabolized but remains unaltered and intact.
Consequently, alcohol becomes a separate and definable component of blood flow.
As blood flows into and through the alveoli (air sacs) in the membranes of the
lungs, carbon dioxide molecules are exchanged for oxygen molecules. Because
alcohol will readily evaporate from a solution and is highly volatile, alcohol
molecules are released with the carbon dioxide molecules during this gas
exchange. Therefore the concentration of alcohol molecules in the alveolar air
of expelled breath is related to the concentration of the alcohol in the blood.
As the alcohol in the alveolar air is exhaled, it can be detected by a breath
alcohol testing device.

Because of this molecular exchange in the lung tissue, the correlation between
alcohol concentrations in the blood stream and the expelled breath can be
established by measuring the exchange rate, or evaporation rate of alcohol in
solution. This rate is then expressed as a constant ratio of blood alcohol
concentration (BAC) to breath alcohol concentration. Using this constant or
fixed ratio with a measured breath alcohol content, equivalent blood alcohol
content can readily be calculated. The ratio of breath alcohol to blood alcohol
is 2,100:1. This means that by volume, 2,100 milliliters (ml) of alveolar air
will contain the same amount of alcohol as 1 ml of blood. If a person's BAC
measures 0.08, it means that there are 0.08 grams of alcohol per 100 ml of
blood.

Electronic measuring devices have been developed to measure breath alcohol
concentration using a fuel cell gas sensor that is specific to alcohol
molecules. The fuel cell sensor has two platinum electrodes with a porous
acid-electrolyte material sandwiched between them. As exhaled air flows past one
side of the fuel cell, the platinum oxidizes any alcohol molecules in the air to
produce acetic acid, protons and electrons.

The formula for reactive oxidation of the alcohol (ethanol) molecule can be
chemically stated. If hydrogen atoms are caused to be stripped by reaction from
the right carbon of ethanol in the presence of oxygen, the end product is acetic
acid, the main component in vinegar. The molecular structure of acetic acid is
then expressed as O = H3C - C - O - H where C is carbon, H is hydrogen, O is
oxygen, the hyphen is a single chemical bond between the atoms and the = symbol
is a double bond between the atoms. When ethanol is oxidized to acetic acid, two
free protons and two free electrons are released from the ethanol molecule.

These two electrons flow through a wire from the platinum electrode in the fuel
cell sensor to an electrical-current meter and then to the platinum electrode on
the other side of the cell. The two protons move through the lower portion of
the fuel cell and combine with oxygen and the electrons on the other side to
form water. The more alcohol from the breath sample that is oxidized, the
greater is the number of free electrons that are produced resulting in the
greater amount of the electrical current that is produced. A microprocessor
measures this electrical current to extrapolate total breath alcohol content
then calculates the equivalent BAC using the constant ratio discussed
previously.

As stated above, the basic technology of these type devices
is essentially similar. A gas specific microchip sensor is used to measure the
amount of a specific target
gas (or hydrocarbon) contained in a specific volume of air (exhaled breath)
by determining the electrical charge produced by the chemical reaction
converting ethanol to acetic acid.
Model quality and cost are differentiated by the
sensor technology employed, processor type, internal
circuit board, features, options and other structural
components.

A micro processor chip on the sensor calculates
the percentage of the target gas contained in the amount of breath sample
analyzed for that specific quantity of breath sample. This percentage (Breath
Alcohol Content) is then converted into equivalent Blood Alcohol Content (BAC)
using standardized logarithms and displayed using various methods; digital,
analog, preset LEDs, audible beeps etc.

In all cases, exposing the sensor to any type
of smoke or oxygen ion generator will produce false positive test results and
inaccurate readings. This includes residual smoke in the lungs of a smoker and
ambient smoke that may be present in the immediate area. Do not use an alcohol
breath analyzer near any type of ion generator including popular air cleaners
and central hvac electronic filtration systems. Smokers must wait a minimum
8-10 minutes after smoking to use a breathalyzer to insure that all residual
smoke is absent from the lungs.

Generally, electronic breath analyzers are
individually pre-calibrated during the final production and assembly process.
Calibration is accomplished using a laboratory simulator device (e.g. GUTH34C ),
flow meter and control sample sets of specific alcohol concentration solutions.
Once the sensor is preset and calibrated, re-calibration should not be necessary
under normal use as each new test procedure is preceded by a microchip recycle
and zero balancing.Accuracy rates are determined in the laboratory
by simultaneously obtaining a breath sample reading from the electronic device
and a drawn blood sample. The device reading is then compared the gas mass
spectrometry reading from the blood sample.

Scientifically, because there are many
independent variables present at any given point in time when a test is given,
no conclusions can be drawn, or correlations made between successive test
procedures. Each test result is independent of other test results and is
specific to the conditions present and the sample analyzed at the exact moment
the test was given. Some of these test specific variables include volume of
breath sample, presence and amount of other gases in the sample, concentration
of alcohol molecules in the mouth, presence and amount of other gases detected
in the immediate environment and others. Example: the amount of breath sample
will probably vary each time a test is performed resulting in a different
reading for each test because of the gas to total volume logarithm. Therefore,
each test result can only be interpreted independently and exclusively of other
test results and correlation between tests should not be attempted nor is
intended with these type of devices. This fact results in a
common misconception and false assumption by users of these devices that they
can "test the tester" by repeatedly blowing into the unit to see if test results
are the same each time, or more erroneously assuming what the test results
should be for any given test event.

Obviously, accuracy
expectations must also be related to the purchase cost of a particular model
breathalyzer. Higher priced models use higher quality components and therefore
can be expected to provide more accurate test results. Lower cost models are not
intended to provide laboratory accuracy or specificity and are more qualitative
and utilitarian in function providing dependable results within the scope for
which they were intended to be used (example: personal versus evidentiary).

In conclusion, users of electronic alcohol
breath analysis devicesshould not expect accuracy rates equivalent to
precisely
controlled laboratory results using flow meter or gas mass
spectrometry equipment. Unexpected readings are almost always the result
of user error, failure to follow device instructions, contamination of the
sample by smoke or other environmental variable, failure to
provide a sufficient breath sample or contamination of the gas
sensor throughmisuse, abuse
or absence of recommended cleaning maintenance. Test results obtained under the many possible
variables of field use are generally assumed to be approximate to actual and not
correlated consecutively.